Robot control method and robot system

Abstract

A robot control method for controlling a robot is provided. The robot has a robot arm and a force detection unit detecting a force applied to the robot arm and grips a target object conveyed on a belt with an end effector provided at the robot arm. The method includes: a gripping step of executing an operation of gripping the target object with the end effector; and a determination step of determining whether the gripping of the target object is normally performed or not, based on a result of detection by the force detection unit in the gripping step.

What is claimed is: 
     
       1. A robot control method for controlling a robot that has a robot arm and a force detection unit detecting a force applied to the robot arm and that grips a target object conveyed on a belt with an end effector provided at the robot arm, the method comprising:
 a gripping step of executing an operation of gripping the target object with the end effector; and 
 a determination step of determining whether the gripping of the target object is normally performed or not, based on a result of detection by the force detection unit in the gripping step, wherein when the gripping of the target object is normally performed, the end effector grips a surface of the target object rather than edge of the surface of the target object or the belt, 
 wherein 
 the end effector is configured to grip the target object by suction, and 
 in the gripping step, a pressing operation of lowering the end effector and pressing the end effector against the target object while performing the suction, and a lifting operation of lifting the end effector while performing the suction after the pressing operation, are sequentially executed, 
 in the determination step, when a maximum value of a force detected by the force detection unit in the pressing operation is less than a first threshold, it is determined that the gripping of the target object is not normally performed, 
 in the determination step, when a magnitude of a force detected by the force detection unit in the lifting operation is less than a second threshold, it is determined that the gripping of the target object is not normally performed. 
 
     
     
       2. The robot control method according to  claim 1 , further comprising:
 a release step of executing an operation of releasing the gripped target object when it is determined in the determination step that the gripping of the target object is not normally performed, wherein 
 in the release step, a timing of releasing the gripped target object is made different between when it is determined that the gripping of the target object is not normally performed in the pressing operation and when it is determined that the gripping of the target object is not normally performed in the lifting operation. 
 
     
     
       3. The robot control method according to  claim 1 , further comprising:
 a reporting step of reporting that the gripping of the target object is not normally performed when it is determined in the determination step that the gripping of the target object is not normally performed. 
 
     
     
       4. The robot control method according to  claim 1 , wherein
 in the determination step, the determination is performed based on information about a force detected over time by the force detection unit. 
 
     
     
       5. The robot control method according to  claim 1 , wherein
 the force detection unit has a quartz crystal force sensor. 
 
     
     
       6. A robot system comprising:
 a robot having a robot arm and a force detection unit that detects a force applied to the robot arm; and 
 a control unit controlling driving of the robot arm so as to grip a target object conveyed on a belt with an end effector provided at the robot arm, wherein 
 the control unit executes an operation of gripping the target object with the end effector, and 
 determines whether the gripping of the target object is normally performed or not, based on a result of detection by the force detection unit, wherein when the gripping of the target object is normally performed, the end effector grips a surface of the target object rather than edge of the surface of the target object or the belt, 
 wherein 
 the end effector is configured to grip the target object by suction, and 
 in the gripping, a pressing operation of lowering the end effector and pressing the end effector against the target object while performing the suction, and a lifting operation of lifting the end effector while performing the suction after the pressing operation, are sequentially executed, 
 in the determining, when a maximum value of a force detected by the force detection unit in the pressing operation is less than a first threshold, it is determined that the gripping of the target object is not normally performed, 
 in the determining, when a magnitude of a force detected by the force detection unit in the lifting operation is less than a second threshold, it is determined that the gripping of the target object is not normally performed.